DR350 Rebuild – No spark issue: Pick up coils test

DIY

As we’ve already tested the ignition and the power source coils, today we’re moving on to the pick up coils test as this is also a common cause of no spark issue.

What the pick up coils actually do?

In the DR 350 we can have one or two pick up coils. It depends on the year of production.
Simplifying things a bit, this pick up coil is generating a signal, when the crankshaft is in a particular position. The generated signal is then transmitted to the CDI unit, which, basing on this signal, decides whether it should fire up a spark on the spark plug. So as you can guess, if the pick up coil is not working properly, then the CDI unit doesn’t know, how to behave, when it’s a a right moment to make a spark and in the result – we don’t get any.

Like in the power source coil test, we’ve got two measurements to make – we will measure the coil’s resistance and the voltage generated by it.

The pick up coils resistance test

We search for the two pairs of cables near the CDI unit – one pair for one coil, as our patient is DR350SP from 1993 and has 2 pick up coils.

The first, bigger coil, is connected to the CDI unit with black and green wires.
Look at the test setup on the DR wiring diagram:

Test setup scheme for the first coil

The second coils is connected with yellow and grey cables.
Here’s a diagram for those:

Test setup for the second pick up coil measurement

All of the interesting wires are in the 4-pin connector.
Let’s have a look.

First pick up coil terminals (black and green wires)

Second pick up coil terminals (yellow and grey cables)

The proper pick up coil resistance for either coil should be in range from 350 to 700Ω. In our case both coils scored 490Ω, so it should be ok.

Traditionally, we filmed the test, so yo can check it out, too.

The voltage measurement

Just like before we tested the resistance, we can check the voltage generated by the pick up coils. We just switch the multimeter to the alternating current mode and have to do some kicking.
Take a look at the schemes:

Test setup scheme for the first coil

Test setup scheme for the second coil

The proper voltage should reach from 0.5 to up to 2V AC during engine startup for both coils.
Though, our multimeter isn’t very accurate and its smallest range is 200V AC. So we just noted that the 0V AC value is changing to some unspecified and not very repeatable value, but from the required range. So eventually we thought to ourselves that the coils probably works ;)